Emergency lighting is required in commercial, industrial, and institutional buildings just as fire extinguishers, smoke alarms and other safety equipment. Three types of emergency lighting are common in such installations: unit equipment, engine generators and central battery systems. Unit equipment falls into two principle types: fluorescent and incandescent.
The fluorescent units are customarily combined with and within a conventional fluorescent lighting unit by merely adding the emergency ballast consisting of a battery, a battery charger, inverter and sensing circuitry adjacent the standard fluorescent ballast. The sensing circuit observes the interruption of normal AC power to the lamp unit and immediately switches on the emergency ballast which powers the light fixture for the required period which, under most state safety codes, is a period of ninety (90) minutes. U.S. Pat. No. 5,004,953 entitled Emergency Lighting Ballast for Compact Fluorescent Lamps with Integral Starters assigned to the assignee of the present invention is illustrative of one type of emergency lighting ballast.
Incandescent emergency lamp systems are usually a self-contained wall or ceiling mounted unit utilizing a sealed beam or quartz lamp and usually consists of a battery, a battery charger, and sensing circuitry. When the power fails to the incandescent system, the sensing circuitry observes the interruption and turns on the self-contained unit for the required time. Incandescent emergency illumination systems are rarely combined with installed lamps except in the central battery systems discussed below.
Central battery systems are utilized to supply power to dedicated circuits on the interruption of normal AC power. Central systems are capable of immediately supplying power to large numbers of lighting fixtures (depending upon total battery resources); however, only for the normal duration of battery supply but at least for the code required 90 minute period. U.S. Pat. No. 4,751,398 for Lighting System for Normal and Emergency Operation of light Intensity Discharge Lamps is illustrative of one type of emergency ballast, in this instance for high intensity lamps, for use with a central battery system.
Engine generators or standby generators are utilized where power must be supplied for a prolonged period of time when normal AC power fails. Such systems normally include diverse circuits rather than individual lamp units, perhaps also including machinery or other apparatus of higher power demands that are conveniently supplied from the standby source. It is usual that several seconds elapse between the AC power failure and the stabilized supply of auxiliary AC power by the generator's system. During this several second lapse of normal AC power, it is not uncommon for light systems to totally extinguish, leaving spaces in darkness for the period of time required for the standby generator to start and come up to stabilized operating speed. Most standby generators are powered by internal combustion engines, the size of which depends upon the size (kilowatts) of the generator to be driven. The procedure on starting is similar to that in starting the familiar lawn mower or automobile wherein, upon a control circuit sensing the loss of AC mains power, signals a starter to crank the internal combustion engine until the ignition catches and the system comes up to the operating speed set by the control circuit.
The present invention in its most simplistic form involves the combination of a standby ballast (bearing some similarity to emergency ballasts for fluorescent systems) with a standby generator system. As will be evident from the description of the preferred embodiments, the similarity between the generator standby ballast and the emergency ballast lie in the inclusion of a battery, a battery charging circuit and inverter driven output circuit; however, the combination of circuit elements and operating parameters of the two devices are remarkably dissimilar.
The prolonged (several second) interruption of power during the failure of normal AC power and the start-up of the engine power generator until it reaches a stable operating condition is significant in several situations. In normal commercial or institutional lighting, the several second dark period (while permitted under local emergency codes) is sufficient for panic and confusion to develop. This period of panic is manifested in a crowd sense by confusion and potential injury from an uncontrolled attempt to exit from a building. Panic is also manifested in a personal sense by anxiety, which may become exacerbated in cardiac or pulmonary distress. By the inclusion of seemingly redundant components of an additional specialized ballast to such as a unit fluorescent lamp including a battery, battery charger, inverter and sensing circuit to a standby generator system, immediate power may be supplied to selected connected loads for the duration of time it takes the generator to start up and stabilize. For applications in individual fluorescent lighting systems or combinations thereof, these generator standby ballasts units are capable of powering the lighting load at its regular level of illumination over relatively short periods of time, such as a minute or so, as the standby generator comes on to line. The generator standby ballast in the fluorescent lighting configuration normally continues the lighting load without noticeable interruption and at a level such that loss of regular AC power from the central source may go undetected as the standby generator comes on line except for alarm devices which otherwise may be tripped.